Within power conversion products, medical equipment and communication equipment, there is a need for high speed digital links that provide high voltage isolation at a low cost. Typically, digital links within power conversion products require a speed of 50 to 100 megabytes per second. Isolation between the input and output of power conversion products is required in the range of 2500 to 5000 volts. Existing solutions for providing a high speed digital isolation link have focused on the use of magnetic pulse couplers, magnetic resistive couplers, capacitive couplers and opto couplers. Typically, this isolation is referred to as “galvanic isolation.” Galvanic isolation is defined as the principle of isolating functional sections of electric systems so that charge-carrying particles cannot move from one section to another, i.e. there is no electrical current flowing directly from one section to the next. Energy and/or information can still be exchanged between the sections by other means, however, such as by capacitance, induction, electromagnetic waves, optical, acoustic, or mechanical means.
Within a magnetic pulse coupler, a driver on one side of the digital link transmits information over the digital link to a detector residing on the other side of the digital link. Between the driver and the detector is a pulse transformer. The pulse transformer provides an electromagnetically coupled transformer between the driver and the detector. The pulse transformer generates a pulse output in response to a provided input from the driver. The input from the driver consists of two pulses, each pulse consisting of a rising edge and a falling edge. In response to a rising edge, the output of the pulse transformer generates a positive pulse. The falling edge of the pulse generates a negative pulse. The pulse transformer circuit has a number of deficiencies. These include start up where the detector will not know at what point the input from the driver has begun, whether high or low, until a first pulse edge has been detected. Additionally, should any error occur in the pulse output of the pulse transformer, the detector has a difficult time determining when to return to a proper state since there may be a long period of time between pulses. An alternative solution involves the use of a magneto resistive coupler. The magneto resistive coupler consists of a resistor and an associated transformer. The resistor has a resistance value that changes responsive to the magnetic flux about the resistor. The transformer detector utilizes a Wheatstone bridge to detect the magnetic flux of the resistor and determine the transmitted data.
Opto couplers are the dominant voltage isolation technology used in the market today. The use of opto couplers is mandated by various safety standards and the increasing complexity of systems requires increased voltage isolation needs. However, the opto couplers have several deficiencies. They are large, slow and their operating characteristics vary with temperature and age. They also require a high power of greater than 5 volts to operate. Switching the LED at higher speed is difficult and takes even more power. Additionally, they are discrete components which are not easily integrated with integrated circuits.
Thus, within isolation technologies there is a need to provide more flexibility with voltage isolation circuitries. The large number of complex system applications that require voltage isolation capabilities have required a number of different solutions such as those described above to be implemented. However, a more flexible solution that is capable of being utilized across a number of different applications would greatly benefit circuit designers requiring improved tools for voltage isolation situations.